Computer plot of the cross-section of an extreme black hole showing the static limit and horizon using the Kerr bookkeeper (Boyer-Lindquist) coordinate r (not R). From inside the horizon no object can escape, even one traveling at the speed of light. Between the horizon and the static limit lies the ergosphere, shaded in the figure. Within this ergosphere everything—even light—is swept along by the rotation of the black hole. Inside the ergosphere, too, a stone can have a negative total energy (Section 10).